Surface coatings adapted to contact tacky adhesive surfaces with a low degree of adherency thereto are needed so that subsequent separation can be effected with an unusually low removal effort. Such coatings have value, for example, as backsize coatings on pressure sensitive adhesive tapes wound in rolls to permit easier unwinding. They also have value as backsize coatings on pressure sensitive adhesive composite wound dressings delivered by a removable carrier, as well as on target strips on disposable diapers. These coatings, which have a low affinity towards contacting adhesives, are referred to as low adhesion backsize coatings.
A low adhesion backsize coating on the top face of a wound dressing provides the ability to apply and remove tapes and other devices over the dressing, thereby enabling the dressing to be used as a platform for those tapes and other devices. For example, the low adhesion backsize coating allows the tapes and other devices to be removed without also removing or disturbing the underlying dressing and allowing additional contamination to reach the wound. An example of such a dressing is that available under the trade designation "TEGADERM" from 3M Company, St. Paul, Minn.
Typically, wound dressings such as this include polymeric films that are extremely thin, flexible, and supple such that they are conformable. They are typically supplied with a releasable protective liner covering the adhesive coated surface of the film. When the liner is removed and/or when the dressing is rubbed against clothing or bed linens, the adhesive coated film can wrinkle and adhere to itself, interfering with the smooth, aseptic application of the dressing to a patient's skin. Thus, in addition to providing a low adhesion backsize coating on the surface of the film opposite the adhesive, it is also desirable to provide the surface with a low coefficient of friction to reduce edge lift of the dressing when rubbed against bed linens or clothing. Such characteristics are desirable for products other than wound dressings as well.
The coefficient of friction of a surface can be modified by mechanical action on the backing before or after the low adhesion backsize is coated, or by incorporating particulate material into the low adhesion backsize coating. Many articles, however, are too soft to be mechanically roughened. Furthermore, it can be difficult to prepare sufficiently thin coatings with particulate material therein and to keep the particulate material homogeneously suspended and uniformly dispersed during the coating process.
It is also often desirable for a low adhesion backsize to have a matte-finish. This is particularly desirable for wound dressings as a matte-finish surface makes the dressing less visible when applied to the skin. As with the coefficient of friction, the finish of a surface can also be modified by mechanical action on the backing or by incorporating particulate material into the low adhesion backsize coating.
Thus, low adhesion backsize coatings with a low coefficient of friction and a matte-finish are still needed, particularly those that are relatively easy to manufacture.